Something special is happening here! These videos are fantastic! I've consumed a ton of HVAC content and attended multi-day training sessions on the topics covered here, but you've managed to bring these concepts down to earth with clear explanations, next-level animations, and excellent narrations If you're in HVAC, you need to see these videos. Thank you for creating such valuable and impressive content. I'll never look at a fan curve the same again, and you even gave us a high altitude breakdown, thank you -another awesome video!
We’re sincerely thankful for your comment. It’s this kind of feedback that motivates us to keep making these. Our aim is to simplify and make these topics click as much as possible.
Impressive work! Never seen an HVAC video done so well - hats off to you guys! Even the way you explain made me think you guys must have rehearsed a lot to deliver the presentation.. overall i thoroughly enjoyed the video!!! Keep making ‘em!
Yep, another 50 mins well spent. Thanks guys. I just noticed, you're making videos since 11 years? Have you ever considered making documentaries on Netflix or similar? You've got some quality content there.
11:15 I don't understand why those units are still used, neither tons nor others hehe it's like we still use hourglasses or projected shadow clocks. But it's an excellent video. Thank you very much for the contribution
Fantastic video. One question, thought. At the Motor Basics section you are saying the reason a 4 pole motor can give out only 1.38hp against full 2hp of a 6 pole motor has to do with the nonlinear relationship between torque and speed. I am not sure myself, but I believe it all comes down to current. With a motor that has fewer poles a VFD will have to lower frequency more than it would with a motor that has more poles. More frequency decrease means more voltage decrease to keep the constant max available motor torque. However, with the same torque * speed = power mechanical, but lower voltage the current will need to be higher to keep v*i = power electrical. So, I guess it's the current that limits the 4 pole 2hp motor to 1.38hp when coupled to that specific fan.
That is correct. But remember the resulting current through the motor will have a lot to do with the voltage out of the VFD (as well as things like slip and how the fields are interacting, or impedance as a whole). Although the VFD doesn't change voltage in a traditional sense, it can change the duration of the pulses that make up the simulated sine wave, and this will change the amount of current flowing through the motor. We have a video that explains this better here ua-cam.com/video/RG3eljmqyq4/v-deo.htmlsi=R5Io5EQkTNSryjqn&t=2431 As explained within this fan video, we do sometimes push that variable voltage so that the motor sees current close to its limit whenever we need to increase power at lower RPMs.
@4:34 Did you insert the probe with the tip opposing the air flow to measure static pressure? I thought this measures total pressure. Static pressure is measured by keeping the probe (hole) perpendicular to the flow.
Yes great question. The probe itself is oriented with the tip facing the airflow. However, the holes that measure the static are not at the tip point, they are on the surface and thus perpendicular to airflow. This ensures velocity/dynamic pressure is not affecting the reading. Next time we will include a graphic to avoid confusion.
3:40 The grid of pitot tubes. Are they simply holes drilled in a common shared tube? Or do they each have their own channel? Is the averaging done mathematically or pneumatically in a shared tube for all the holes? I could imagine air flowing into some holes but blowing out others.
The holes seem to be in a common shared pipe, so the pressure there is the average of the total pressures. The static pressure appears to be taken at only one point. Since the velocity depends on the square root of the dynamic pressure, using average pressures may not give an accurate average velocity. In this case, it does not matter because the measurement location is quite ideal and the variation between points is small. In field conditions, the dynamic pressures (the difference between the total pressure and the static pressure) are taken separately at these points with a Pitot tube.
Just finished the Plotting Horsepower lines section of the video, Is the real world performance of the Fan curves also tested to verify the calculated results? Sorry if this is answered later.
Great question which we didn't address. Yes you are correct, the performance will be tested at different points and rpms and any adjustments to the theoretical curves will be made then.
They can change pulse duration within each simulated sine wave, with a similar effect to a voltage increase. The voltage of each pulse is constant though. For more info, here's a good section of video ua-cam.com/video/RG3eljmqyq4/v-deo.htmlsi=R5Io5EQkTNSryjqn&t=2431
Wrong! Brake-horse-power is the horse power above and beyond that which is needed to overcome the engine friction and is that power available to the output. Or in other words it’s the power output which requires external brakes to arrest it.
Something special is happening here! These videos are fantastic! I've consumed a ton of HVAC content and attended multi-day training sessions on the topics covered here, but you've managed to bring these concepts down to earth with clear explanations, next-level animations, and excellent narrations If you're in HVAC, you need to see these videos. Thank you for creating such valuable and impressive content. I'll never look at a fan curve the same again, and you even gave us a high altitude breakdown, thank you -another awesome video!
We’re sincerely thankful for your comment. It’s this kind of feedback that motivates us to keep making these. Our aim is to simplify and make these topics click as much as possible.
If only someone would do a video like these about fabric ductwork…
Impressive work! Never seen an HVAC video done so well - hats off to you guys!
Even the way you explain made me think you guys must have rehearsed a lot to deliver the presentation.. overall i thoroughly enjoyed the video!!!
Keep making ‘em!
Yep, another 50 mins well spent. Thanks guys.
I just noticed, you're making videos since 11 years? Have you ever considered making documentaries on Netflix or similar? You've got some quality content there.
Always surprising quality content and good explanation. See as a compliment your videos are addictive.
Amazing. This was the most simplest way I have seen it explained yet. Keep them coming!
I am addicted to this content. Good refresher! Thank you!
This is so fascinating. I've always found airflow intriguing. This channel is very informative. Thanks for sharing.
11:15 I don't understand why those units are still used, neither tons nor others hehe it's like we still use hourglasses or projected shadow clocks.
But it's an excellent video. Thank you very much for the contribution
Fantastic video.
One question, thought.
At the Motor Basics section you are saying the reason a 4 pole motor can give out only 1.38hp against full 2hp of a 6 pole motor has to do with the nonlinear relationship between torque and speed.
I am not sure myself, but I believe it all comes down to current.
With a motor that has fewer poles a VFD will have to lower frequency more than it would with a motor that has more poles. More frequency decrease means more voltage decrease to keep the constant max available motor torque. However, with the same torque * speed = power mechanical, but lower voltage the current will need to be higher to keep v*i = power electrical.
So, I guess it's the current that limits the 4 pole 2hp motor to 1.38hp when coupled to that specific fan.
That is correct. But remember the resulting current through the motor will have a lot to do with the voltage out of the VFD (as well as things like slip and how the fields are interacting, or impedance as a whole). Although the VFD doesn't change voltage in a traditional sense, it can change the duration of the pulses that make up the simulated sine wave, and this will change the amount of current flowing through the motor. We have a video that explains this better here ua-cam.com/video/RG3eljmqyq4/v-deo.htmlsi=R5Io5EQkTNSryjqn&t=2431
As explained within this fan video, we do sometimes push that variable voltage so that the motor sees current close to its limit whenever we need to increase power at lower RPMs.
@4:34 Did you insert the probe with the tip opposing the air flow to measure static pressure?
I thought this measures total pressure. Static pressure is measured by keeping the probe (hole) perpendicular to the flow.
Yes great question. The probe itself is oriented with the tip facing the airflow. However, the holes that measure the static are not at the tip point, they are on the surface and thus perpendicular to airflow. This ensures velocity/dynamic pressure is not affecting the reading. Next time we will include a graphic to avoid confusion.
3:40 The grid of pitot tubes. Are they simply holes drilled in a common shared tube? Or do they each have their own channel? Is the averaging done mathematically or pneumatically in a shared tube for all the holes? I could imagine air flowing into some holes but blowing out others.
The holes seem to be in a common shared pipe, so the pressure there is the average of the total pressures. The static pressure appears to be taken at only one point. Since the velocity depends on the square root of the dynamic pressure, using average pressures may not give an accurate average velocity. In this case, it does not matter because the measurement location is quite ideal and the variation between points is small. In field conditions, the dynamic pressures (the difference between the total pressure and the static pressure) are taken separately at these points with a Pitot tube.
This is so d**n awesome!
Bro damn isn't a swear word
Excellent
Are you saying that the VFD is best running in V/f mode rather than Sensorless Vector mode for fans?
These guys have no idea how to make a bad video.
I had to read this like 3 times lol
Me too :)
Just finished the Plotting Horsepower lines section of the video, Is the real world performance of the Fan curves also tested to verify the calculated results?
Sorry if this is answered later.
Great question which we didn't address. Yes you are correct, the performance will be tested at different points and rpms and any adjustments to the theoretical curves will be made then.
didn't know vfds can also change voltage
They can change pulse duration within each simulated sine wave, with a similar effect to a voltage increase. The voltage of each pulse is constant though.
For more info, here's a good section of video ua-cam.com/video/RG3eljmqyq4/v-deo.htmlsi=R5Io5EQkTNSryjqn&t=2431
Wrong! Brake-horse-power is the horse power above and beyond that which is needed to overcome the engine friction and is that power available to the output. Or in other words it’s the power output which requires external brakes to arrest it.